Heavy weight paper bags are frequently employed for containing, storing and shipping flowable, fine powdery materials and small sized granular products, such as starch, food products, chemicals, cement and the like. By virtue of the flowable character of these products, such bags are filled by inserting a filler spout of a dispensing machine into an opening of the bag, and the product is delivered from a source thereof through the spout into the bag. Many types of the products packaged in this manner may contain dust, or are themselves "dusty" and are easily suspended in the air during movement of the product, as during filling of the bag.
Because dusty portions of the products are easily suspended within the air, filling operations are sometimes messy, and can even present a health hazard to personnel due to the ambient air being polluted by the product. In addition when the filled bags are being transported, the vibrations of the carrier, truck, train and the like cause the fine powdery material to sift out through the filler opening part of the bag. Consequently, attempts to prevent sifting the bags' contents through the valve have been made and special valves have been devised in the past to tightly fasten the filler openings of the bag to the dispensing spout, which valves are adapted to substantially prevent the escape of product from the bag once the dispensing spout is removed from the filler opening. In order to increase production efficiency, these prior art filler valves have been adapted to automatically seal the filler opening after the filling process has been completed.
Prior art bags of the type mentioned above comprise a tubular paper bag closed at both ends, at least one end having a plurality of flaps folded over to define a passageway in the end of the bag which presents an opening at one corner thereof. The bottom flaps are hingedly interconnected to permit the bag to be folded into a flat condition, wherein the walls defining the passageway collapse into face to face, abutting relationship. A flexible, tubularly shaped sleeve, formed from one mil low density polyethylene is secured within the passageway and is coextensive with the latter. The entire length of the sleeve is secured to, and between, the bottom flaps. The sleeve may be secured to a backing panel which is interposed between opposing bottom panels of the bag. The dispenser spout is inserted into the sleeve forming the valve and product is dispensed into the bag. After the bag is filled, the weight of the product in the bag presses downwardly against one of the bottom flaps which squeezes the sleeve between opposing flaps, thereby closing the sleeve and, thus the valve.
The primary problem associated with the prior art bags of the type described above is related to the fact that the sleeve valve used in such bags was not "sift-proof" with respect to the product; i.e. the fine powdery material and small sized product within the bag had a tendency to sift out around and through the sleeve, thereby escaping from the bag. This was due in part to the fact that wrinkles in the sides of the plastic sleeve were created by the filling operation. These wrinkles formed channels on both sides of the walls of the sleeve through which the product could escape.
Accordingly, it is an important object of the present invention to provide an improved valve for flexible bags which is automatically closable and permits filling of the bag with product, but which eliminates the problem of sifting of the product through the sleeve after the bag is filled.
As a corollary to the foregoing object, a further object of the present invention is to provide an improved sleeve valve which eliminates the problem of wrinkling in the material forming the sleeve valve during the filling operation.
Another object of the invention is to provide a sleeve valve which automatically folds against itself after the filling operation is complete in order to positively close the filler passageway through the valve.
A still further object of the invention is to provide an improved valve for flexible bags of the type described above wherein the flexible sleeve is securely held on the bag and is prevented from pulling away therefrom during the filling operation.